The aim of the research plan is to study the genetics of the translational apparatus in B subtilis. Our laboratory has previously shown that most of the DNA base sequences complementary to 5S, 16S and 23S ribosomal rRNA are found in the same region of the subtilis chromosome as several mutations conferring resistance to certain antibiotics which affect ribosomal function. We have subsequently shown that some of these mutations conferring resistance in B. subtilis also cause changes in specific ribosomal proteins or are very closely linked to genes which code for ribosomal proteins. In addition, we have demonstrated that genes for elongation factors EF-Tu and EF-G map in this area. On the basis of this genetic evidence and on various kinetic data dealing with the synthesis of ribosomal components, we postulate that the genetic determinants for rRNA and ribosomal protein are coordinately controlled in B. subtilis. To provide evidence for the concept of ribosomal operons: We are mapping markers which confer resistance to ribosomally active antibiotics. This will be accomplished by cloning segments of the B. subtilis chromosome containing genetic determinants for the translational apparatus using E. coli plasmids or bacteriophage.